 编译时错误 javac: Command not found  包含javac编译器的路径变量设置不正确。  HelloWorldApp.java:3: Method printl (java.lang.String) not found in class java.io.PrintStream. System.out.printl (“Hello World!”); ^  方法名printl不正确， HelloWorldApp.java:1: Public class HelloWorldapp must be defined in